1. Field of the Invention
The present invention relates to the structure of a semiconductor device which improves a mechanical strength between a bump electrode formed on the semiconductor device and a semiconductor device substrate.
2. Description of the Related Art
Up to now, in mounting of a semiconductor device, packaging means has frequently been employed. However, with an increase in need for downsizing an electronic device and making it light-weight, a portable electronic device such as a portable telephone or a digital camera is required to realize higher-density mounting. At present, a small-sized package such as BGA or CSP has been applied, and further a flip chip mounting where a mounted circuit substrate or the like and a bump electrode are connected directly to each other in a bear chip state is utilized as means for realizing the high-density mounting.
The flip chip mounting is conducted by a method of connecting a bump electrode 1 on a semiconductor device shown in FIG. 5 directly to a mounting circuit substrate or the like. A bump electrode used for connection is formed by the following procedures 1 to 5.
1. An insulating film 7 is deposited on a semiconductor substrate 8.
2. A metal wiring 4 made of Al or the like is patterned on the insulating film 7 as a connecting or wiring layer.
3. The metal wiring 4 is coated with a protective film 3 made of silicon nitride or the like so that an opening is formed only at a portion where an electrode is to be formed.
4. A barrier metal 2 made of Cr or the like is deposited by sputtering.
5. A bump electrode 1 made of solder or the like is formed by an electrolytic plating method.
In general, the semiconductor devices fabricated by the above-described manner have been widely employed in flip chip mounting.
However, in order to realize higher-density mounting, the above semiconductor device is required to reduce an electrode area and a bump diameter. However, if the electrode area and the bump diameter are reduced, a contact area of the bump electrode with the semiconductor device substrate is reduced, resulting in such a problem that the mechanical strength of the bump electrode is insufficient.
The present invention has been made to solve the above problem, and therefore an object of the present invention is to provide a semiconductor device which improves the mechanical strength of a bump electrode and a semiconductor device substrate, thereby being capable of achieving higher-density mounting.
In order to achieve the above object, according to the present invention, there is provided a semiconductor device characterized in that an irregularly stepped pattern is formed on a wiring layer, an insulating film, a protective film, etc., in a region under the bump electrode except for a protective-film opening portion.
The irregularly stepped pattern is an asperity under the bump electrode or a plurality of salient on insulation layer.